Food Commodities Soybeans
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How much oilseed production does soybean count for?
Soybeans account for about 50% of the global oilseed production
What climates are best for soybean production?
Temperate climates are better suited for soybean production
What type of soil is best for soybeans?
- Prefers soil pH ranging from 6-6.5
- Alkaline soils; may be necessary to adjust pH with acid treatment (usually acetic acid)
What makes soils alkaline?
Due primarily to the presence of CaCO3
How does acid treatment change soil?
Treatment with acid will use up the CaCO3 and when the latter is depleted, the pH of the soil falls until the desired level
How are acidic soils produced?
Acidic pH due to emissions producing oxides of C, S, and N into the atmosphere that become part of rain
What is the shape of soybeans?
Spherical to elongated and flat
Describe the soybeans used for oil production
The beans used for oil production tend to be yellowish in color, small in size and spherical in shape
Describe the soybeans used as vegetables
The beans used as vegetables tend to be larger in size, elongated in shape and of varied colours (yellow, green, brown, black)
Why are mature seeds left on the plants?
- Mature seeds are left on the plants to dry out until a moisture content of 12-13% is reached.
- 12-13% moisture content is the best or storage stability of the beans as well as the handling characteristics
What happens if the soybean moisture content is >13%?
Makes beans susceptible to mould and fungal growth
What happens if the moisture content of soybeans is <12%?
Moisture content <12% makes beans very brittle and break easily
How is the composition of soybeans expressed and why?
Composition of soybeans is expressed in moisture-free basis because the seeds are practically dried when they are picked and stored
What is a dicot?
Has 2 seeds leafs covered by an outer layer known as the testa
For every ton of crude soybean oil produced how much oil meal is produced?
Approximately 4.5 tons of soybean oil meals with a protein content of about 44%
What is responsible for the rapid growth in soybean production?
Mostly due to the sharp increase in the US production between 1950 and 1970, and to the introduction of the soybean to Brazilian agriculture in the 1960s
When are soybeans planted?
Late spring to early summer
When is full maturity attained?
What is the cotyledon?
the cotyledon represents ~90% of the seed weight and contains practically all the oil and protein in its cells
Where is the oil located within the soybean?
In the cotyledon
What is the general structure of a soybean?
Consists of the seed coat (testa), 2 cotyledons, the radicle and plumule
How is soybean oil obtained and used?
Obtained by solvent (hexane) extraction, used as cooking oil, but also used in the chemical industry as starting material for bio-diesel, inks, plasticizers, crayons, paints, and even candles
How is soy meal obtained and used?
Ground flakes after oil extraction, used for feed (cattle, swine, poultry, and fish)
What are soy flours?
Refers to defatted soybeans where special care was taken during solvent removal in order to minimize denaturation of the protein (minimum 50% protein content), starting material for protein enriched soy products
How much protein is in soy protein concentrate?
SPC has 65% to 85% protein content
How is soy protein concentrate manufactured?
Usually manufactured by using alcohol to remove the soluble carbohydrates from the de-oiled soy flakes, resulting in a protein with low solubility, good water holding capacity, but incapable to forming gels or emulsifying fat. Traditional alcohol-washed soy concentrates are used
What is the composition of sucrose and what type of linkages are there within the molecule?
- disaccharide of glucose and fructose
- glycosidic bond
- The glycosidic bond for the sucrose is sometimes referred to as an a-b-1-2 bond, because there's an alpha-OH from the glucose bonding to a beta-OH from the fructose, and we're going from the #1 carbon on the glucose to the #2 carbon on the fructose
- not a reducing sugar
What is the composition of raffinose and what type of linkages are there within the molecule?
- trisaccharide of galactose, fructose, and glucose
- galactose and glucose are linked by alpha-1,6-glycosidic bond and glucose is linked to fructose by an alpha,beta-1,2-glycosidic bond
- not a reducing sugar
What is the composition of stachyose and what type of linkages are there within the molecule?
- two α-D-galactose units, one α-D-glucose unit, and one β-D-fructose unit sequentially linked as gal(α1→6)gal(α1→6)glc(α1↔2β)fru
- reducing sugar (=has an aldehyde group or is capable of forming one through isomerism, allowing the sugar to act as a reducing agent)
What are the 2 types of soybean protein?
- Storage (80%)
- Bioactive (20%)
What is the solubility of soybeans?
High solubility in salt solutions but dissolves to some extent in H2O
What is the solubility of soybean proteins in different pHs?
Proteins very soluble at extreme pHs but with limited solubility at pH 4.2-4.5
What is the separation of proteins based on?
Based on size (weight)
What are 2S proteins?
- Proteins with sizes ranging from 8-20 kDa
- Alpha conglycinin (storage protein) and soybean trypsin inhibitor (bioactive protein)
- Alpha-conglycinin elicits allergic type reactions in some individuals
What are 7S proteins?
- Molecular weights ranging from 120-150 kDa
- main proteins include beta and gamma- conglycinins (storage proteins) and enzymes like LOX, amylases, cysteine, proteases and urease
What are the most abundant types of proteins in soybeans?
- 7S and 11S are the most abundant and account for about 70% of the soy proteins
- Ratios in which the 7S and 11S occur (0.5:3.0) are distinct features of different varieties of soybeans and is used as a basis for classification
How much storage proteins are used as a nutrient/energy source?
80% storage proteins serve as nutrient/energy source
What foods are soybean proteins comparable to?
Soybean protein of comparable nutritive value as egg or meat proteins
What is LOX?
Why must LOX be removed from soybeans?
Can cause breakdown of soybean lipids to form carbonyl compounds that impart objectionable 'beany' flavour or taste to soy products so the need for LOX to be removed or inactivated
Why is LOX used in wheat flour production?
LOX breaks down carotenoid pigments and this feature is exploited in decolourizing of wheat flour
What does urease do?
Breaks down proteins (uric acid) to liberate NH3, which can impart objectionable flavour to soybeans and its products
Why is urease used as a measure of the effectiveness of heat treatment?
- Urease is heat stable and its inactivation is used as a measure of the effectiveness of heat treatment for soybeans
- If heat treatment is not adequate, enzymes like LOX and urease can survive and cause objectionable flavour
What are the germination enzymes?
- Lytic enzymes
- Other biological components
What do lytic enzymes do?
Break down cell walls to permit germination
What is Soybean trypsin inhibitor?
- A proteolytic enzyme found only in animals
- Causes pancreas to overproduce trypsins
- (Why? Trypsin is an enzyme produced by your pancreas used in digesting protein, and is critical for antibody production. An inhibitor is something that disables. Think of it like having one foot on the gas and another on the brake of your automobile at the same time. Your car’s engine would blow-up. So a trypsin inhibitor will irritate your pancreas, stressing it to produce hormones when it can’t, leading to decreased oxygenation from the irritation. Soy prevents the protein you eat from being fully utilized and digested. Your immune system can’t get fueled with proper antibodies and lymphocytes — a double whammy. Therefore, soy is cancer-causing to your pancreas and cancer of the pancreas is typically a death sentence.)
What are lectins?
- Protein molecules with strong adhesive properties
- They are known to cause agglutination of blood cells
Why are soybean lectins referred to as agglutins?
They can bind to the surfaces of the intestine at the distal end and interfere with intestinal metabolsim
How are SBTIs and lectins denatured?
- Both SBTI and lectins are denatured by the heat treatments normally applied to soybeans
- Thus, their harmful effects are curtailed by heat treatment
Other than heat treatment, how can lectins be denatured?
High pressure treatment can also denature lectins, however this technique is not used commercially to denature lectins because of the expense
What are isoflavones?
- Non nutrients
- Some elicit hormonal effects in mammals (including humans)
- Some elicit anti-oxidant and/or anti-cancer effects
Why are soybean oils not extracted by pressing?
- Not efficient
- Costly and low yield
How is commercially produced soybean oil extracted?
What are the steps to extracting soybean oil?
- Solvent extraction
What happens during the cleaning step of soybean oil extraction?
- Undesirable components like twigs, stones, empty or free hulls are removed
- Magnetic separation to remove small pieces o metals that may become part of the beans during harvesting
What happens during the de-hulling step of soybean oil extraction?
Entails cracking beans open to remove the seeds and exclude the hulls
What happens during the flaking step of soybean oil extraction?
- Involves heating the seeds in water to facilitate slicing into flakes
- This is important to increase surface area for the extraction step with the solvents
What solvent is used to extract soybean oil?
How is solvent extraction done?
Soyflakes are treated with hexanes by soxhlet extraction- to recover oil in the solvent phase while the solid residue (mainly proteins and carbohydrates) are retained
What happens during the purification of soybean oil?
- Filtration to remove undesirable components
- Filtration to remove insoluble material
- Degumming by hydrating phosphatids dissolved in oil with water and with acid (phosphoric acid)
- The phosphatids hydrate, expand and agglomerate to form large peptides that are removed in a separation step using separations
- Alkaline treatment to form soaps with the FFA
- Water wash to remove soaps
- Vacuum drying to remove moisture
How are FFAs removed from soybean oil?
- Alkaline treatment to form soaps with FFA
- Water wash to remove soaps
How is soybean oil degummed?
- Hydrating phosphatids dissolved in oil with water and with acid (phosphoric acid)
- The phosphatids hydrate, expand, and agglomerate to form large peptides that are removed in a separation step using separations
How is soybean oil deoderized?
Steam stripping or vacuum, evaporation of oil to exclude volatiles
How is bleaching done to soybean oil?
- To remove coloured pigments that may be present in the oil
- Usually involves heat treatment to degrade the pigments which are then adsorbed onto adsorbents like activated charcoal or bentonite
How is purified oil treated?
- May be treated further to remove waxes and triacylglycerides. These latter components have high melting points, so by slowly cooling the purified oil, we can get them to crystallize out and separate
- This process is known as WINTERIZING or WINTERIZATION
Why is soybean oil often hydrogenated?
- Hardens the oils to various degrees
- Hydrogenation stabilizes the oils (via reduction in degree of unsaturation in the oils)
What results from partial hydrogenation?
- Results in reduced unsaturation and formation of cis-and trans- isomers
- Trans fats are considered not desirable for health
Describe the lipid profile of Soybean oil
- High in PUFAs 587-60%
- MUFA- 23-26%
- SFA- 16%
What PUFAs are found in soybean oil?
- Linoleic acid (50%)
- Linolenic acid (7-10%)
What MUFAs are found in soybean oil?
Oleic acid (23%)
What SFAs are found in soybean oil?
- Palmitic acid (10%)
- Stearic acid (4%)
What is done with the solid residue left over after solvent extraction?
This solid residue may be treated to remove solvents (de-solventization) and fed as soy meal to animals (cattle, fish, poultry, etc)
What are whole fat soy flours made from?
Made from the whole non de-fatted beans
How are defatted soy-flours treated (2 ways)?
- Produced with low-mild heat treatment so it retains enzymes like LOX in active forms
- Produced with regular high heat treatment
How is soy protein concentrate produced?
Produced by washing defatted soy flour with ethanol to remove CHO
What is an important characteristic o the soybean plant?
- N-fixing capacity through symbiosis with soil bacteria
- It is estimated that up to 50% of the total nitrogen of the plant may be supplied by the nitrogen fixing mechanism
What are some CHO present in soybeans?
How is the nutritional quality of protein evaluated?
- Evaluated by its chemical score (by comparing its essential amino acid composition to that o a standard reference protein such as whole egg protein
- Chemical score of soybean protein is 70%
Why is soybean better than most plant proteins?
Exceptionally rich in lysine and can sere as a valuable supplement to sereal foods where lysine is a limiting factor
How are soy proteins characterized?
By their solubility in various media
What is the isoelectric region of soybean protein as a whole?
What are globulins characterized by?
The bulk of soybean proteins are globulins, characterized by their solubility in salt solutions
What happens when soy protein is centrifuged?
Soy protein is heterogeneous, and when centrifuged (at pH 7.6 and 0.5 ionic strength), produce fractions 2S, 7S, 11S, 15S.
How are soy proteins fractioned?
Soy proteins are fractionated by ultracentrifugation, gel filtration and electrophoresis
What is LOX responsible for in soybean oil?
Responsible for oxidative rancidity in soybean oil
What are the two types of SBTIs?
- Kunitz inhibitor (20kDa)
- Bowman-Birk inhibitor (80kDa)
How are the effects of SBTIs eliminated?
When soybean is properly heated
How do SBTIs affect the GIT of the animal?
Impair protein digestibility and utilization
How do SBTIs affect the pancreas?
- Increase pancreatic secretion and hypertrophy of the pancreas
- Increased secretion of enzymes into the GIT represents an internal loss of protein
How does soybean lectin affect the GIT?
Can bind to the surfaces in the distal part of the small intestine to damage small intestine villi and disrupt small intestinal metabolism
How are oligosaccharides in soy beans digested?
Not digestible and produce gas and cause bloating and abdominal discomfort
How can HPP alter soybean proteins?
HPP is capable of altering the molecular structure of antigens (proteins) which are the starting point of food allergies
How are whole soybeans utilized?
- Roasted whole soybeans and their flour are used as ingredients in confectionery products and snacks
- The immature whole green soybeans are also consumed as a vegetable
******The mature dry soybeans are seldom used as cooked vegetable even in the traditional soybean consuming areas. Why is that?
First, because of their high protein content and low starch content, soybeans require much longer cooking than most other beans, generally 5-6 hours without pressure (but only 25-30 minutes at 15 pounds pressure), and even after this they never get as soft as most beans. Also, this long cooking uses lots of fuel, which has always been relatively expensive in densely populated areas. Moreover, the water in China is generally hard (rich in calcium), which further increases the required cooking time. Second, boiled or baked whole soybeans are more difficult to digest than most other soyfoods and than some other dry beans; the oligosaccharides they contain, which are removed in the processing of most soyfoods, can cause flatulence. And third, most East Asian people prefer the flavor and versatility of other soyfoods. (People in countries that have not traditionally consumed soybeans often describe them as having a "beany" flavor). Yet throughout East Asia, whole dry soybeans have long been used in certain dishes at certain times.
How is soy flour made?
Made from powdered roasted soybeans
What are the principle uses for full-fat soy flour?
Principle use of FFSF and grits is in the bakery industry
What are the 2 types of full-fat soy flour?
- Enzyme-active: prepared without heat treatment and used mostly in bakery products (white bread and rolls), mainly for its LOX activity
- Enzyme-inactive: prepared with heat treatment and used in the heavier types of cake batters, such as sponge cakes and pound cakes)
What are some common uses for defatted soy flour?
Used as a protein supplement in bread, tortillas, pasta and other cereal products
What are some common uses of soy protein concentrate?
Bakery products, meat products, and as stabilized dispersions in milk-like beverages and simulated dairy products
How is soy milk made?
- Dry beans are rehydrated by soaking in water overnight (min 3 hrs)
- Beans are then wet milled with water to form a slurry
- The resulting slurry or puree is heated close to boiling for ~15-20 min (to improve nutritional value by heat inactivating soybean trypsin inhibitor, improve its flavour and to sterilize the product)
- The boiled slurry is cooled and filtered to remove the insoluble residue (soy pulp fiber or okara)
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